Internal combustion engines with infra-red detection

ABSTRACT

A method of checking and/or varying the fuel to air mixture ratio of an internal combustion engine comprises measuring the intensity of the infra-red emission from the flame during combustion in the combustion chamber by an infra-red photosensitive device and feeding the signal to an indicator, such as a meter, an audible device, or a &#39;&#39;&#39;&#39;magic eye&#39;&#39;&#39;&#39; device, and/or to automatic control means for effecting any adjustment that may be necessary of the fuel/air mixture ratio. Apparatus comprises a &#39;&#39;&#39;&#39;Colourtune&#39;&#39;&#39;&#39; spark plug provided with a tubular adaptor comprising an insulating sleeve with a longitudinal slot for the lead of the plug from one end fitting over the transparent core of the plug, and the other end of the sleeve being joined to one end of a tubular metal shield the other end of which houses a detector cell for infra-red emission mounted on an insulated plug eccentrically with respect to the insulating sleeve on the opposite side of the axis to the slot for the plug lead.

United States Patent [191 Swithenbank et al.

[ Aug. 21, 1973 INTERNAL COMBUSTION ENGINES WITH INFRA-RED DETECTION [75 Inventors: Joshua Swithenbank, I-lathersage,

near Sheffield; David Shawflfaylor; Michael Stuart Bolton, both of Sheffield, all of England [73] Assignee: Gunsons Colorplugs Limited [22] Filed: May 22, 1972 [21] Appl. No.: 255,651

Primary Examiner-Harold A. Dixon Attorney-Lowe & King 5 7 ABSTRACT A method of checking and/or varying the fuel to air mixture ratio of an internal combustion engine comprises measuring the intensity of the infra-red emission from the flame during combustion in the combustion chamber by an infra-red photo-sensitive device and feeding the signal to an indicator, such as a meter, an audible device, or a magic eye" device, and/or to automatic control means for effecting any adjustment that may be necessary of the fuel/air mixture ratio. Apparatus comprises a Colourtune" spark plug provided with a tubular adaptor comprising an insulating sleeve with a longitudinal slot for the lead of the plug from one end fitting over the transparent core of the plug, and the other end of the sleeve being joined to one end of a tubular metal shield the other end of which houses a detector cell for infra-red emission mounted on an insulated plug eccentrically with respect to the insulating sleeve on the opposite side of the axis to the slot for the plug lead.

9 Claims, 3 Drawing Figures INTERNAL COMBUSTION ENGINES WITH INFRA-RED DETECTION This invention relates to intemal'combustion engines and in particular to a method'and apparatus for checking and if necessary varying the fuel/air mixture ratio.

It is well-known that in setting the mixture ratio one should be aiming at the stoichiometric mixture to provide not only maximum power output from a given quantity of fuel but also minimum pollution by avoiding discharge of unbumt gases. One device aimed at assisting the fuel/air mixture adjustment is a spark plug (sold under the Trade Mark Colortune") which has a transparent core which enables the colour of the flame in the combustion chamber during combustion to be observed. The fuel/air mixture is adjusted to the transition point (which gives the stoichiometric mixture) between,

the fuel rich mixture, a,yellow flame, and the fuel weak mixture, a blue, flame. The accuracy of this technique is limited by the difficulty or otherwise encountered in setting the exact transition point and also this technique cannot be used where the engine is utilising a gaseous fuel because of the complete absence of a yellow flame.

The object of the present invention is to provide an improved method and apparatus for varying the fuel/air mixture ratio employing the principle of flame observation.

According to the present invention a method of checking and if necessary, varying the fuel/air mixture ratio of an internal combustion engine, comprises measuring the intensity of the infra-red emission from the flame during combustion in the combustion chamber by an infra-red photosensitive device and feeding the signal from such device to an indicator means and possibly also to automatic control means for effecting any adjustment that may be necessary of the fuel/air mixture ratio based on the result provided at the indicator means.

Thus, as a characteristic of the flame of combustion of an internal combustion engine is that the infra-red emission from the flame (CO and H varies with the fuel air mixture ratio and reaches a peak close to the stoichiometric mixture ratio one can readily check the fuel/air mixture ratio by (for example if the indicator means gives a visual indication) graduating the indicator to show a correct" mixture ratio at a condition of a maximum emission of infra-red radiation and similarly showing weak" or rich" mixtures dependent upon the degree of infra-red emission.

In its simplest form the method of the invention includes the step of adjusting the mixture manually. However it is perfectly possible to have the adjustment effected automatically by feeding the signal to automatic control means for the fuel/air mixture, as mentioned above.

According to another aspect of the invention, apparatus for carrying out the above-defined method, comprises a photo-sensitive device for measuring the intensity of the infra-red emission from the flame of combustion in a combustion chamber, an amplifier for the signal from the photo-sensitive device and an indicator.

means to which the amplified signal is fed.

For manual adjustment of the mixture ratio the above apparatus is basically all that is required, but if it were desired to effect the adjustment automatically, e.g., for the engine of a road vehicle then the invention provides for the addition of an automatic control means operated by signals derived from the intensity of the infrared emissions. The fuel flow may be modulated slightly so that an appropriate system, such as an electronic phase sensitive detector, may determine whether an increase or decrease in fuel/air ratio is required;

The photo-sensitive device may receive infra-red emission from the flame through a Colortune" spark plug provided with a tubular adaptor comprising a sleeve of insulating material with a longitudinal slot for the lead of the plug, one end of the sleeve being adapted to fit over the transparent core of a Colortune spark plug and the other end of the sleeve being joined to one end of a tubular metal (e.g., copper) shield the other end of which houses a detector cell for infra-red emission, the detector cell being eccentrically mounted on an insulated plug on the opposite side of the axis to the slot for the plug lead, so that the plug lead doesnot lie across the path of emission from the flame to the detector cell. The tubular metal shield, which serves to screen the detector cell from the high voltage on the plug lead, may be provided with an endplate at its end joined to the insulating sleeve, with a hole in the endplate in line with the detector cell, and the hole in the endplate may be covered with a'metal gauze (e.g., copper) to reduce interferencefrom the spark plug itself. The detector cell may be connected to the core of a coaxial cable, one end of the braid of which is connected to earth (e.g., the vehicle earth if the vehicle battery is positive earth) the other end of the braid being trapped between the insulated plug and the metal shield. The tubular metal shieldis preferably provided with an insulating sheath.

The indicator could be a meter, or an audible device, or a conventional magic eye device.

The above method and apparatus is suitable not only for internal combustion engines employing a liquid fuel, but also for engines employing a gaseous fuel.

One embodiment of apparatus according to the invention and a modification thereof will now be described, by way of example only, with reference to the accompanying drawings, in which FIG. 1 is a perspective view of the apparatus, with cables indicated as shortened for clarity;

FIG. 2 is a longitudinal section of a part of F 16.1; and

FIG. 3 is a block circuit diagram of the apparatus of FIG. 1 and also shows the modification.

In FIG. 1 a Colortune spark plug 1 has a tubular adaptor 2 with a cable 3 and plug 4 to fit a socket 5 on a meter box 6, the latter having a power cable 7 with crocodile clips 8 for attachment to a battery (e.g., a vehicle battery not shown). The tubular adaptor 2 (see also FIG. 2) comprises a sleeve 9 of insulating material with a longitudinal slot 10 for the lead 11 of the plug 1, one end 12 of the sleeve 9 being adapted to fit over the transparent core 13 of the spark plug and the other end 14 of the sleeve being joined to one end 15 of a tubular metal (e.g., copper) shield 16 the other end 17 of which houses a detector cell 18 for infra-red emission, the detector cell being eccentrically mounted, on an insulated plug 19, on the opposite side of the axis to the slot 10, so that the plug lead 11 does not lie across the path of emission to the detector cell from a flame in a combustion chamber (not shown) into which the spark 20 at its end 15 joined to the insulating sleeve 9, with a hole 21 in the endplate in line with the detector cell, and the hole 21 may be covered with a metal (e.g., copper) gauze to reduce interference from the spark plug itself. The tubular metal shield is provided with an insulating sheath 22. The cable 3 is a coaxial cable the core 23 of which is connected to the detector cell 18. One end of the braid 24 of the cable 3 is connected to earth through the meter box 6 and one of the crocodile clips 8 (e.g., to the vehicle earth if the vehicle battery is positive earth) and the other end of the braid is trapped between the insulated plug 19 and the metal shield 16.

As shown in FIG. 3 the meter box 6 includes an impedance converter 25, a variable gain amplifier 26, and a meter 27, the sensitivity of the unit being adjusted by a knob 28 so that a suitable order of reading on the meter is obtained. FIG. 3 also indicates the optional addition of automatic control means 29 for the: fuel/air ratio, without which automatic control means the fuellair ratio is adjusted manually until a maximum reading is obtained on the meter 27 (for one particular setting of the sensitivity control knob 28) from maximum emission of infra-red radiation at the correct mixture ratio.

What we claim is l. A method of checking and controlling the fuel to air mixture ratio of an internal combustion engine comprising measuring the intensity of the infra-red emission from the flame during combustion in the combustion chamber by an infrared photosensitive device, feeding the signal to an indicator means, and varying the fuel to air mixture ratio until the indicator means receives a peak signal from the infra-red photo-sensitive device.

2. A method as in claim 1, wherein the signal from the infra-red photo-sensitive device is aiso fed to automatic control means for effecting such variation of the fuel to air mixture ratio as may be necessary for the indicator means to receive a peak signal from the infrared photo-sensitive device.

3. Apparatus for use in checking and controlling the fuel to air mixture ratio of an internal combustion engine comprising a photo-sensitive device for measuring the intensity of the infra-red emission from the flame of combustion in a combustion chamber, an amplifier for the signal from the photo-sensitive device, an indicator for utilizing that amplified signal, and means to vary the fuel to air ratio in accordance with the signal read on said indicator, whereby the peak signal from said device may be obtained.

4. Apparatus as in claim 3, wherein said means to vary the ratio includes means for feeding the amplified signal from the infra-red photo-sensitive device, and automatic control means for receiving said signal and varying the fuel to air mixture ratio until the indicator means receives a peak signal from said infra-red photosensitive device.

5. Apparatus as in claim 1, wherein the photosensitive device is adapted to receive infra-red emission from the flame through a spark plug provided with a tubular adaptor comprising a sleeve of insulating material with a longitudinal slot for the lead of the plug, one end of the sleeve being fitted over the transparent core of the spark plug, and the other end of the sleeve being joined to one end of a tubular metal shield the other end of which houses a detector cell for infra-red emission, the detector cell being mounted on an insulated plug eccentrically with respect to the sleeve of insulating material on the opposite side of the axis to the slot for the plug lead, so that the plug lead does not lie across the path of emission from the flame to the detector cell.

6. Apparatus as in claim 5, wherein the detector cell is connected to the core of a coaxial cable, one end of the braid of which is connected to earth, the other end of the braid being trapped between the insulated plug and the metal shield.

7. Apparatus as in claim 5, wherein the tubular metal shield is provided with an insulating sheath.

8. Apparatus as in claim 7, wherein the tubular metal shield is provided with an endplate at its end joined to the insulating sleeve, with a hole in the end plate in line with the detector cell.

9. Apparatus as in claim 8, wherein the hole in the endplate is covered with a metal gauze. 

1. A method of checking and controlling the fuel to air mixture ratio of an internal combustion engine comprising measuring the intensity of the infra-red emission from the flame during combustion in the combustion chamber by an infra-red photosensitive device, feeding the signal to an indicator means, and varying the fuel to air mixture ratio until the indicator means receives a peak signal from the infra-red photo-sensitive device.
 2. A method as in claim 1, wherein the signal from the infra-red photo-sensitive device is also fed to automatic control means for effecting such variation of the fuel to air mixture ratio as may be necessary for the indicator means to receive a peak signal from the infra-red photo-sensitive device.
 3. Apparatus for use in checking and controlling the fuel to air mixture ratio of an internal combustion engine comprising a photo-sensitive device for measuring the intensity of the infra-red emission from the flame of combustion in a combustion chamber, an amplifier for the signal from the photo-sensitive device, an indicator for utilizing that amplified signal, and means to vary the fuel to air ratio in accordance with the signal read on said indicator, whereby the peak signal from said device may be obtained.
 4. Apparatus as in claim 3, wherein said means to vary the ratio includes means for feeding the amplified signal from the infra-red photo-sensitive device, and automatic control means for receiving said signal and varying the fuel to air mixture ratio until the indicator means receives a peak signal from said infra-red photo-sensitive device.
 5. Apparatus as in claim 1, wherein the photo-sensitive device is adapted to receive infra-red emission from the flame through a spark plug provided with a tubular adaptor comprising a sleeve of insulating material with a longitudinal slot for the lead of the plug, one end of the sleeve being fitted over the transparent core of the spark plug, and the other end of the sleeve being joined to one end of a tubular metal shield the other end of which houses a detector cell for infra-red emission, the detector cell being mounted on an insulated plug eccentrically with respect to the sleeve of insulating material on the opposite side of the axis to the slot for the plug lead, so that the plug lead does not lie across the path of emission from the flame to the detector cell.
 6. Apparatus as in claim 5, wherein the detector cell is connected to the core of a coaxial cable, one end of the braid of which is connected to earth, the other end of the braid being trapped between the insulated plug and the metal shield.
 7. Apparatus as in claim 5, wherein the tubular metal shield is provided with an insulating sheath.
 8. Apparatus as in claim 7, wherein the tubular metal shield is provided with an endplate at its end joined to the insulating sleeve, with a hole in the end plate in line with the detector cell.
 9. Apparatus as in claim 8, wherein the hole in the endplate is covered with a metal gauze. 